1. Field of the Invention
This invention relates to a method for the preparation of microspheres, involving fluidized bed drying.
2. Description of Background and Related Art
The instant invention provides for a method for the preparation of microspheres wherein the microspheres are dried in a fluidized bed. The microspheres of the instant invention may encapsulate any kind of active agent, such as an antigen, adjuvant, peptide, polypeptide, hormone, antibiotic, and so on.
Polymer matrices for forming microspheres are described in the literature. U.S. Pat. Nos. 4,917,893 and 4,652,441 disclose a microcapsule produced by preparing a water-in-oil emulsion comprising an inner aqueous layer containing a water-soluble drug, a drug-retaining substance, and an oil layer containing a polymer substance; the inner or aqueous layer is thickened or solidified to a viscosity of not lower than about 5000 centipoises. The resulting emulsion is subjected to in-water drying. U.S. Pat. No. 4,954,298 discloses the production of microcapsules by preparing a water-in-oil emulsion composed of a water-soluble drug-containing solution as the inner aqueous phase and a polymer-containing solution as the oil phase, dispersing the emulsion in an aqueous phase and subjected the resulting water-in-oil-in-water emulsion to an in-water drying, wherein the viscosity of the water-in-oil emulsion used in preparing the water-in-oil-in-water emulsion is adjusted to about 150 to about 10,000 centipoises.
The microspheres of the art have typically been dried by v acuum drying or lyophilization. These methods are time consuming and often result in degradation, or "cracking", of the microspheres so dried.
Accordingly, it is an object of the invention to provide a method for drying microspheres.
It is another object to provide a drying procedure for microspheres that reduces the amount of time for drying and the amount of degradation of the microspheres.
These and other objects will be apparent to those skilled in the art.